title: Comparison of exhaled endogenous particles from smokers and non-smokers using multivariate analysis.
abstract: BACKGROUND
  Smoking, along with many respiratory diseases, has been shown to induce airway inflammation and alter the composition of the respiratory tract lining fluid (RTLF). We have previously shown that the phospholipid and protein composition of particles in exhaled air (PEx) reflects that of RTLF. In this study, we hypothesized that the composition of PEx differs between smokers and non-smokers, reflecting inflammation in the airways.
  
  
  OBJECTIVE
  It was the aim of this study to identify differences in the phospholipid composition of PEx from smokers and non-smokers.
  
  
  METHODS
  PEx from 12 smokers and 13 non-smokers was collected using a system developed in-house. PEx was analysed using time-of-flight secondary ion mass spectrometry, and the mass spectral data were evaluated using multivariate analysis. Orthogonal partial least squares (OPLS) was used to relate smoking status, lung function and pack years to the chemical composition of RTLF. The discriminating ions identified by OPLS were then used as explanatory variables in traditional regression analysis.
  
  
  RESULTS
  There was a clear discrimination between smokers and non-smokers according to the chemical composition, where phospholipids from smokers were protonated and sodiated to a larger extent. Poor lung function showed a strong association with higher response from all molecular phosphatidylcholine species in the samples. Furthermore, the accumulated amount of tobacco consumed was associated with variations in mass spectra, indicating a dose-response relationship.
  
  
  CONCLUSIONS
  The chemical composition of PEx differs between smokers and non-smokers, reflecting differences in the RTLF. The results from this study may suggest that the composition of RTLF is affected by smoking and may be of importance for lung function.
authors.affiliation: Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden. anna.bredberg@amm.gu.se
authors.forename: Anna
authors.initials: A
authors.lastname: Bredberg
authors.forename: Mats
authors.initials: M
authors.lastname: Josefson
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Almstrand
authors.forename: Jukka
authors.initials: J
authors.lastname: Lausmaa
authors.forename: Peter
authors.initials: P
authors.lastname: Sjövall
authors.forename: Anna
authors.initials: A
authors.lastname: Levinsson
authors.forename: Per
authors.initials: P
authors.lastname: Larsson
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air / Q000032:analysis*; D001944:Breath Tests / Q000379:methods*; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D015999:Multivariate Analysis; D009569:Nitric Oxide / Q000032:analysis*; D012907:Smoking / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide